Specialty Metals ProductionSpecialty Metals ProductionConsiderations for SOFCConsiderations for SOFC

Thomas J. MatwayGeneral Manager

Precision Rolled Strip® ProductsATI Allegheny Ludlum

6th Annual SECA WorkshopApril 18 - 21, 2005

IntroductionIntroduction

• Specialty metals industry• Specialty metals products and forms• Processing of specialty metals• Product development considerations• Raw material challenges

IntroductionIntroduction

• Specialty metals industry• Specialty metals products and forms• Processing of specialty metals• Product development considerations• Raw material challenges

Focus on high volume production & low costLinking SOFC system designer with material designer

Specialty Metals IndustrySpecialty Metals Industry

• US consumption of stainless steel (all product forms) was 2.5 million tons in 2004*

• ATI Allegheny Ludlum produces over 700,000 tons per year of flat-rolled products;

stainless steel, specialty stainless, nickel-base alloys, titanium, and other specialty metals such as multi-layered clad products

* SSINA news release, 03/18/2005www.ssina.com

Specialty Metals by CompositionSpecialty Metals by Composition

• Ferritic stainless steels (Fe-Cr)

• Austenitic stainless steels (Fe-Ni-Cr)

• PH stainless steels (Fe-Ni-Cr)

• Iron-base superalloys (Fe-Ni-Cr)

• Nickel-base superalloys (Ni-Cr-Fe)

• Cobalt-base superalloys (Co-Cr-Ni)

• Reactive metals– Titanium– Zirconium

– Niobium– Hafnium

– Tantalum

Specialty Metals by CompositionSpecialty Metals by Composition

• Interconnects (ferritics, Ni alloys)

• Heat Exchangers (specialty steels, Ni alloys)

• Reformers (Ni alloys, etc.)

• Other Balance of Plant

Specialty Metals by CompositionSpecialty Metals by Composition

• Interconnects

• Heat Exchangers

• Reformers

• Other Balance of Plant

The commercially competitive SOFC system would likely require a combination of high temperature specialty materialsMaterial selection would likely be driven by performance, cost, and material availability considerations

Stainless SteelsStainless Steelsand Niand Ni--BaseBaseAlloysAlloys

Ni

FeCrferritic stainless steels

austeniticstainless steels

duplexstainless steels

nickel-basesuperalloys

Austenite (γ) stabilized byC, N, Ni, Mn, Cu, Co

Ferrite (α) stabilized byAl, Ti, V, Si, Cr, Mo, W, Ta

allo

ys la

ck h

eat an

d co

rros

ion

resist

ance

brittle

Ferritic Stainless SteelsFerritic Stainless Steels

Fe-CrType 409

Mo

↑ strength, creep resistance↑ oxidation, corrosion resistance

↓ stability

potential catastrophic oxidation

Nb, Ti, Ta, W

↑ strength, creep, corrosion resistance

AL409HP™ stainless steel

Cr

↑ strength, creep, oxidation, corrosion resistance

↓ stability

Types 430, 446

AL444™ AL436S™ stainless steels

“superferritics”E-BRITE® alloy, AL 29-4C® alloy,

SEA-CURE® alloy

AL439HP™, AL441HP™stainless steels

Al↑ ↑ oxidation resistance↓ manufacturability

AL 409ALMZ™

(external coating)ALFA-I®, ALFA-II® alloys,

FeCrAl alloys SOFC Interconnect AlloysTypically tend to resemble relatively lean superferritic stainless steels with specific

constraints on minor alloy chemistry

™ Trademarks of ATI Properties, Inc.® Registered Trademarks of ATI Properties, Inc.

SuperalloysSuperalloys

Ni-Cr(γ phase)

Precipitation strengthened alloys

Al + Ti (γ’ Ni3Al phase)ALTEMP® A286 Alloy (Fe-Ni)

ALTEMP® X–750, ALTEMP® 263 Alloys, Waspaloy (Ni)

Nb + Fe (γ’’ Ni3Nb phase)ALTEMP® 718 Alloy

Solid–solution and carbide-strengthened alloysCr, Co, Fe, Mo, Ta, W

Corrosion-resistant alloysAL22™ Alloy, ALLCORR® Alloy

Heat and corrosion-resistant alloysALTEMP® 600, ALTEMP® 601, ALTEMP® 625, ALTEMP® HX Alloys

SOFC Interconnect Alloys

Ni and Ni base alloys have shown promising surface

properties. Issues exists relative to CTE and cost

™ Trademarks of ATI Properties, Inc.® Registered Trademarks of ATI Properties, Inc.

Specialty Metals by Product FormSpecialty Metals by Product Form• Flat Products

– SheetTypically < 3/16” thick and > 24” wide

– StripTypically < 3/16” thick and < 24” wide

– Precision Rolled Strip® ProductTypically < 0.015” and other specialized products at heavier gaugesProduced to tight tolerances other restrictions, Foil typically < 0.005”

– PlateTypically > 3/16” thick and > 10” wide

• Long Productsbar, billet, rod

• Otherspipe, tubing, wire castings, forgings, powder

® Registered Trademark of ATI Properties, Inc.

Primary Production OverviewPrimary Production Overview

electric arcfurnace

argon-oxygendecarburizationvessel

slabs

continuouscasting

ingot casting

ingot heating (soaking pits)

hot rollingingot to slab

blooming mill

shear

Melting

six-stand hot strip mill

HRB coil

doubled HRB coil (optional)

slab reheat

hot rolling slabs to bar

scale breaker

roughing mill

hot rolling bar to coil

Coil Processing OverviewCoil Processing OverviewA&P coil grinding

HRBcoil

B&P A&Pintermediatecold rolling

conditioning

intermediateannealing

package and ship

coil grinding

temper rolling

Bright annealing

A&P

finish rollingfinal

annealingTandem mill

4-high reversing mill

Sendzimir mill

post-processing

slit-to-width

cut-to-length

MeltingMelting• Primary melting practices

– EAF electric arc furnace– EAF/AOD argon oxygen decarburization– VIM vacuum induction melting

• Re-melting practices– ESR electro-slag remelt– VAR vacuum arc remelt

• Premium melting practices– EB-CHR electron beam– PAM plasma arc melting

EAF / AOD SteelmakingEAF / AOD Steelmaking• Vast majority of stainless steel is produced

via EAF/AOD process• Electric arc furnace (EAF)

– Scrap steel charge melted via arc struck between metal and consumable graphite electrodes

– Allows for versatile raw materials usage (computer modeling of composition and cost)

– Resulting molten steel transferred via ladle to the AOD for refining

Electric Arc FurnaceElectric Arc Furnace

ATI Allegheny LudlumElectric Furnace Shop - Brackenridge Works

Hot Metal TransferHot Metal Transfer

ATI Allegheny LudlumAOD Melt Shop - Brackenridge Works

AOD RefiningAOD Refining• Major breakthrough in stainless steel

production (1970’s)• Primarily a refining stage• Permits the production of clean stainless

steel low in carbon, sulfur (ppm level) from relatively impure raw materials

• Works with a charge of hot metal transferred from the EAF, scrap steel, and selected additions

ArgonArgon--Oxygen DecarburizationOxygen Decarburization

ATI Allegheny LudlumAOD Melt Shop - Brackenridge Works

AOD Refining StagesAOD Refining Stages• Gas blow

– Mixture of Ar, O2, N2 injected into molten steel through submerged tuyeres

– Carbon content lowered by oxidation– Final carbon content controlled primarily by chromium

content (C and Cr at equilibrium)

• Deoxidation– Bubbles of inert gases tend to carry off dissolved oxygen– Increase (Ar,N2):O2 ratio as melting proceeds– Actively deoxidize using reactive additions (Al, Ti, Ca, Si)

AOD Refining StagesAOD Refining Stages• Slag reduction

– Metallic elements (Cr, Mo, Ni) tend to oxidize and partition to slag

– Si, Al added to reduce these oxides to near 100% recovery

• Chemical analysis– On-line during melting– Allows for late corrections to alloy chemistry

• Tapping• Ladle stirring and late additions of highly

reactive alloying elements

Alternative Primary Melting MethodsAlternative Primary Melting Methods• Vacuum induction melting (VIM) (Ni, Co)

– Induction melting in a refractory crucible– Poured into an ingot mold– Used for high-quality, clean melting of alloys containing

reactive additions

• Plasma arc melting (PAM) (Ti)– Melting in an inert gas under an electric arc from a non-

consumable electrode– Melts a wide variety of feedstock forms

• Electron beam cold hearth melting (Ti)– Material melted by electron beams– Melts a wide variety of feedstock– Long residence time and bath geometry contribute to

removal of LDI and HDI

RemeltingRemelting• Higher alloy-content materials prone to segregation

• Second and possibly third melt cycle used to homogenize alloys prone to segregation and/or improve cleanliness of finished ingot

• Primary ingot generally used as electrode

• Typically used for critical quality parts (rotating components; jet engines, pharmaceutical, etc.)

• Process control (e.g. melt rate, temperature profile) critical to achieving desired end result

ElectroslagElectroslag RemeltingRemelting (ESR)(ESR)• Air melting under a slag blanket

• Electrode typically positioned above a fixed, water cooled copper mold

• Melt zone separated from solid electrode by molten slag blanket

• Melting proceeds by passing electric current through the slag blanket between the solid electrode and the molten pool

• Molten metal droplets pass through the slag, resulting in refinement and inclusion control

Vacuum Arc Vacuum Arc RemeltingRemelting (VAR)(VAR)

• Electrode typically positioned above a fixed, water cooled copper mold

• Melting proceeds by striking an arc between the solid electrode and the molten pool

• Can use a fabricated electrode rather than a solid ingot (Ti, Zr)

CastingCasting• Hot metal is solidified in a controlled manner into

a desired shape

• Continuous casting– High-aspect ratio single strand cast in a fixed mold with

water-cooled oscillating sides– Mold fed from above by a tundish– Enables several melt heats of continuous casting

• Ingot casting– Several large low-aspect pieces cast in removable molds– Bottom poured from ladle into a series of runners– Only used when concasting is not practical or technically

feasible– Generally lower yield than concasting

Continuous CastingContinuous Casting

ATI Allegheny LudlumContinuous Caster - Brackenridge Works

Ingot CastingIngot Casting

ATI Allegheny Ludlum - Brackenridge Works

Hot RollingHot Rolling• Ingots are reheated and bloomed to slab

• Slabs are reheated and rolled to bar

• Bar is fed directly to a hot rolling mill

• Types of hot rolling mills– Continuous mill (hot strip mill)– Reversing mill– Steckel mill (reversing mill with integral coil

heating stations on either side)

Hot Hot RollingRolling

ATI Allegheny LudlumHot Strip Mill - Brackenridge Works

Cold RollingCold Rolling• Reversing mills• Sendzimir mill

– “Z” - mill– Small diameter work rolls surrounded by larger

back-up rolls– Coiling stands provide tension– Large reductions possible on strong materials– Active shape and gauge control– Material can be produced as wide as 60” and

as thin as 0.0007” (18 microns)

Cold RollingCold Rolling

AnnealingAnnealing• Continuous process

– “Strand” annealing– End of one coil joined to start of next– Material hangs free in furnace (caternary)– Highest throughput

• Batch process– Box / bell annealing– Typically used for long exposures in controlled

atmosphere– Entire coil annealed as a whole

AnnealingAnnealing• Air annealing

– Strip tends to oxidize– Followed by descaling treatments– Heavy gauge products

• Reactive / inert atmospheres (bright anneal)– Hydrogen– Cracked ammonia– Nitrogen– Endothermic / exothermic gases– Light gauge stainless and alloy products

• Vacuum annealing– Typically a batch process– Generally used for alloys incompatible with

bright annealing (e.g. Ti)

AnnealingAnnealing

ATI Allegheny RodneyBright Anneal

Waterbury WorksATI Allegheny LudlumAnneal and Pickle Line - Leechburg Works

SlittingSlitting• Coils cut to desired width using circular

slitting knives with very tight tolerances

• Widths controlled by building up knives and spacers on an arbor

• Edge shape and burr controlled by slitting and can be altered by dressing

• Slit mults can be wrapped around a spool (wide) or oscillate-wound (narrow)

SlittingSlitting

Optimal Production ProcessOptimal Production Process

• Lowest cost to meet application requirements

• Highest yield and material availability

• Production flexibility

• Low Raw Material Volatility

Product Development ProcessProduct Development Process

• Technical Review & Initial Specification

• Small Lot Production & Evaluation

• Pilot Production Scale Manufacturing

• Product Evaluation

• Process Optimization

• Flow Path & Supply Chain Definition

Product Development ProcessProduct Development Process

• Technical Review & Initial Specification• Small Lot Production & Evaluation

Product Development ProcessProduct Development Process

• Product Evaluation• Process

Optimization

Optimal Production ProcessOptimal Production Process

electric arcfurnace

argon-oxygendecarburizationvessel

six-stand hot strip mill HRB coil

slabs

continuouscasting

slab reheat

hot rolling slabs to bar

scale breaker

roughing mill

hot rolling bar to coil

Air Melting

Optimal Production ProcessOptimal Production Process

B&P

package and ship

HRBcoil

Bright annealing

A&P

A&P

finish rolling

intermediatecold rolling

final annealing

conditioning

Sendzimir mill

intermediateannealing

slit-to-width

Raw Material ChallengesRaw Material Challenges

Raw Material ChallengesRaw Material Challenges

Raw Material ChallengesRaw Material Challenges

Raw Material ChallengesRaw Material Challenges

SummarySummary• Integrated SOFC Systems are likely to

Contain a Wide Spectrum of Specialty Metals

• Those Metals will be Tailored to the Specific Application Based on Performance and Cost

• Specialty Materials Provider can Further Benefit the SOFC System Developer by Acting as a Technology Resource capable of Product Development, Application Support as well as Full Scale Production and Supply

• Across a Wide Range of Specialty Materials